In Germany, there continues to be an intensive debate about the financing of social insurance by contributions and/or taxes. How should the financing be (adequate according to different tasks) and how is it done and is there a mismatch between the type of the task and the type of financing? This mismatch can have negative economic effects. The paper discusses arguments in favour of a financing that is adequate regarding the tasks and types of expenditure in several branches of social insurance in Germany. Effects of inadequate financing are discussed. A special focus is on the effect of social insurance contributions on non-wage labour costs. Different possibilities towards adequate financing are outlined. These alternatives are closely linked to the question, which concept should be relevant to design a social insurance scheme. The volume of inadequate financing in total as well as in several branches of social insurance in Germany is outlined. Finally, it is discussed what the economic effects would be, if in case of an unchanged sum of social insurance expenditure the financing structure would partially be shifted from social insurance contributions to taxation and what could be the “price”, if financing remains inadequate.